Elwyn waller and charles augustus sniffin



UNITED STATES PATENT OFFICE.

' ELWYN VVALLER AND CHARLES AUGUSTUS SNIFFIN, OF NElV YORK, N. Y.

METHOD OF CONCENTRATING oREs.

SPECIFIGATIONforming part of Letters Patent No. 509,058, dated November21, 1893. Application filed May 2, I893. Serial No.472.787. (Nospecimens.)

To aZZ whom it may concern:

Be it known that we,-ELWYN WALLER and OHARLns AUGUSTUS SNIFFIN, bothcitizens of the Unlted States, and residents of the city, county, andState of New York, have invented certain new and useful Improvements inMethods. of Concentrating Ores, of which the following is aspecification.

The methods ordinarily employed for concentrating ores depend chiefly orentirely upon the difierence of specific gravity between the ore or freemetal and the gangue with WhlOll the ore is associated, whereby, whenthe finely pulverized material is agitated with air or water, or by somemechanical means, the material having the higher specific gravity isconveyed to or deposited in one place, while the portion having thelower speclfic gravity is conveyed to or deposited in another place.Thus a rough sort of separatlon 1s effected. and the major portion ofthe gangue disposed of. These methods are designed to separatethemetal-bearing ore or free metal from the gangue or rock, and not toseparate one metal in the ore from another metal contained therein. Someores are found vto contain both a base metal and a precious metal, thepercentage of baser metal being usually much the larger, and in order toconcentrate the precious metal, it is desirable to remove the basermetal from the crude ore or material. Our invention has reference moreespeclally to this latter class of concentration. Our method ofconcentrating has for its obect to remove from the ore certain portionsthereof which portions are brought into solution, thus affordingcompounds valuable in the arts, while other portions of the valuablematerial are thus concentrated in the residue or undissolved gangue.This method may be employed either separately, or in conjunction withsome other method or methods of separation and concentration, dependentupon specific gravity alone.

With the carbonate ores of lead, containing the mineral cerussite moreor less mixed with other minerals, we are able by our process, whensilver is present, to dissolve out the lead and leave the silver in theresidue with the other undissolved substances, the result belngaconcentration of the silver in such argentiferous ores. It may bedesirable to remove all of the lead, or to leave a portion of the leadwith the silver in the residue from the concentration, in order tofacilitate the extraction of the silver present; and the proportion oflead left in the residue may be regulated either by the strength of thesolvent solution used, or by the length of time which said so lution ispermitted to act, or by the proportion of the solvent to the amount ofore treated,or by the character of the solvent employed.

The solvents we have found very effective are acetic acid and solutionsof acetate of lead. Practically all acetates, as well as acetic acid,when in aqueous solution, will, with the aid of heat, dissolve out thelead from lead carbonate ores. The action of all is the same .in kindbut different in degree.

Our process may be carried out by mixing together in a suitable vesselacetic acid,water and argen tit'erous ore containing lead carbonate, andheating this mixture up to the point of ebullition. The acetic acidcombines with the lead, forming lead acetate, and gaseous carbonic acidis set free. The solution of lead acetate is drawn off and theargentiferous residue reserved for treatment by any known process forthe extraction of the silver.

It will be obvious that no exact proportions of the several ingredientscan beprescribed, nor are any exact proportions essential: If theproportion of acid is equal to or greater than one hundred and twentypounds of real acetic acid to two hundred and seven pounds of lead, ascarbonate, in the ore, neutral lead acetate will be formed and will passinto solution. If the proportion of lead in the ore is greater than thatgiven above, basic lead acetates will be formed by the action of theneutral acetate upon the lead carbonate remaining. This action issomewhat slower than when acetic acid is used, but at a boilingtemperature the action is rapid, becoming gradually slower as thesolution becomes more and more basic.

When a solution of the neutral lead acetate is subjected to prolongedboiling, some of the acetic acid passes on with the steamand wateryvapor and may be condensed and utilized again as a solvent forconcentration, on a fresh lot of ore. By this treatment the solotion isconverted into a solution of basic lead acetate.

If acetic acid be used in a proportion greater than one hundred andtwenty pounds of real acid to two hundred and seven pounds of lead ascarbonate in the ore, and if, as may sometimes occur, the ore containssilver carbonate, some silver acetate may be formed and go intosolution. In such a case the silver may be put back into theundissolvedresidue' by the addition to the charge of a small amount ofmetallic lead in a subdivided condition. The action which takes place isthe substitution of lead for the silver in the solution, the silverseparating out in the metallic state. The carbonic acid evolved in theprocess will be collected and utilized, and in order to recover thisacid the process is carried on out of contact with the air.

The action of other acetates than lead acetate, at the boilingtemperature, will be to form, chiefly, neutral lead acetate; a portionof the carbonic acid from the carbonate ore is driven off with the steamand a portion combines with the base of the acetate employed to form acarbonate.

We do not claim the manufacture of acetates bysprinkling the ground orewith acetic acid and exposing them to the air, nor do We claim therecovery of metals from ores by the combined action of the oxidizinginfluence of air and thatof acetic acid. Our process excludes the airand has for its object the'con centration of the precious metal in theresidue by the extraction of the baser metal, lead.

Having thus described our invention, we clai-m-- 1. The herein describedmethod of concentrating argentiferous lead carbonate ores which consistsin dissolving out lead from the ore with the aid of acetic acid, real orcombined, and water, out of contact with the air whereby the lead andcarbonic acid elimi- 'nated from the ore are rendered capable ofutilization in the arts, and the undissolved silver is concentrated inthe residue, substantially as set forth.

2. The herein described method of concentrating argentiferous leadcarbonate ores which consists in removing the lead, or the major portionthereof, from the one with the aid of water, acetic acid and heat, andout of contact with the air whereby the undissolved silver isconcentrated in the residue, substantially as set forth.

3. In the treatment of lead carbonate ores, the method of recoveringacetic acid from neutral acetate solutions, which consists in boilingthe solution, whereby it is converted into a solution of basic leadacetate, and condensing the vaporized acetic acid,.substantially as setforth. I

In witness whereof we have hereunto signed our names in the presence oftwo subscribing witnesses.

' ELWYN WALLER.

CHARLES AUGUSTUS SNIFFIN.

Witnesses:

HERBERT BLossoM, J AS. KING DUFFY.

